Self-scraping hearth for gas generators and other furnaces



Oct- 18 1927.

TREFOIS SELF SCRAPING HEARTH FOR GAS GENERATORS AND OTHER FURNACES FiledJune 16, 1925 Patented a. 18, 1921.

UNITED STATES 1,645,671 PATENT OFFICE.

LEON armors, or rename, BELGIUM.

SELF-BGBAPING HEARTH FOR GAB GENERATORS AND OTHER FURNACES.

Application filed June 16, 1925, Serial 80. 37,588, and in Belgium June24, 1924.

All engineers are in agreement upon the necessity for keeping inmovement the 1gnited mass of fuel with a view to preventing theformation of flame passages which ro- 6 duce carbon dioxide andclinkers, an to thus assist the descent of the charges.

The difliculties encountered are well known. They are chiefly due to theincomplete removal of the ashes, particularly those 10 which remainimprisoned against the wall of the shaft and which produce theobjectionable formation known as the effect of the walls. I

Several means are already known:

1. In revolving ash pits, the form of the central head through which theblowing is effected is varied greatly, the chief effect of whichvariation is to cause the clinkers to be broken up, certain apparatusbein in addition provided at the base of the s aft with a lining forprotecting the latter.

These devices act upon the lower zone of the la er and oppose thedescent of the ashes which accumulate near the walls due to the producedby the rotation rotary movement of the ash pit.

2. Revolving hearths with the surface of varied form, for raising thefuel. Their efficienc is Very low due to the fact that,

as in t e previous case, the rotar movement compresses the mass againstt e Walls and keeps the part which is nearest the latter stationary.

3. Mechanical stirrers in the form of arms raking the upper zone of thefuel. They serve no other purpose than to close up the flame holesproduced and do not combat the causes of them.

4. Finally, revolving shafts, which have the advantage of releasing themass of fuel from the effect of the friction which keeps it stationaryand which, combined with one or other of the means indicated under 1 and2 give the desired result. If the cost of construction were notprohibitive there would be no need to seek any other device.

The object of this invention is to obtain the same result by means of asimple revolving hearth the profile of which is such that it separatesthe mam of fuel from the walls by raising it, thus counteracting theeffect-of friction which is, in the devices mentioned hereinbefore under1, 2 and 3, on the contrary greatly increased b the centrifugal effectof the rotation. or this purpose, according to the invention, eachprojection provided on the upper face of the hearth consists of adistorted surface the bounding lines of which bear on the one hand onone pomt of the axis of rotation on the hearth and on the other upon aperipheral curve havingthefath of a helix or the like traced 1n passingrom a level on the same plane or higher than that of the center of thehearth and rising as it winds in a direction opposite to the directionof rotation of the hearth so that the movement of rotation neutralizesthe effect of friction of the fuel upon the walls and ensures thedesired regular descent of the charges.

The accompanying drawing illustrates by way of example one form of theinvention.

, Figure 1 is a vertical section through the center of the hearth;

Figure 1 is a plan view of the hearth;

Figure 2 is a diagrammatic representation of the forces acting on thefuel;

Figure 3 is a radial section through one of the ash outlets.

1 is a frame provided with a rolling track 2 carried upon rollers 3,guided by rollers 4. The same is provided with teeth 5 by means of whichit may be driven by a pinion not shown, the shaft of which, extendingoutside of the ash pit, is driven in any suitable man ner.

The frame 1 carries the hearth proper 6, which receives the charge offuel.

The hearth 6 consists of two or more sections having a distorted surfacethe shape of which is determined by the displacement 01 a generatingline having oneend on a point of the axis of rotaton of the hearth, andthe other upon a portion of a helix traced upon the inner surface of theshaft in passing from a plane at the same level or higher than that ofthe center of the hearth and rising as it winds in a direction oppositeto the direction of rotation of the hearth.

If the whole arrangement is rotated in the direction of the arrow, thefuel will be raised by each of the sections in turn, and by suitablychoosing the pitch of the helix, (see Fig. 2) the raising effort aneutralizes to the desired extent, in strength and direction, theresultant b of the vertical force a exerted by the weight of the fueland the horizontal force d which is the sum of the horizontal componentdue to the charge of fuel and to the force due to the movement. ofrotation.

The force causing the friction upon the wall being thus neutralized,there is nothing to oppose the uniform descent of the charges, while atthe same time the whole mass is kept in continuous movement.

In order to completely evacuate the ashes, they must not only be removedregularly along the length of the walls but alsoat the same time from aslarge a number of ints as possible upon the surface of comustion so thatthe said ashes may have the smallest possible distance to travel inorder to reach the outlet,

These outlets for the ashes .must also be arranged in such a way thatthe ashes fall out 0 them naturally that is to say in the direction ofthe path determined by the resultant of the forces in action.

Finally, each of these outlets must be exactly proportioned to the zoneit has to serve.

The conditions are obtained in the present invention by the formation ofoutlet apertures 7 (see Figs. 1 1 and 3) provided over the whole surfaceof the hearth and arranged upon concentric circles, proportional innumber to the surfaces comprised between them.

This arrangement allows of a number of air inlets, and effects, at thesame time a practically perfect contact between the fuel and theoxidizing agent.

The inlet orifices of the passages through which the ashes are evacuatedare circularly distributed and are formed in the hearth in a directionparallel to 'the resultant of the forces acting on the ashes in such away that they fall through naturally.

In this way the forces which obstruct the descent of the charge andwhich are neutralized by the projecting sections provided at the upperpart" of the revolving hearth are therefore efliciently em loyed inorder to produce an automatic an normal evacuation of the ashes,

What I claim as m invention and desire to secure by Letters atent is:

1. A revolving hearth for gas furnaces and the like comprising aplurality of sections, each of said sections comprising a surfacegenerated by a line one end of which pivots at a point at the hearthcenter and the other end follows an outer directmg curve at the hearthperiphery, said outer curve being at a higher level than the pivotalcenter, whereby the fuel is prevented from moving outward under theaction of centrifugal force.

2. A revolving hearth for gas furnaces and the like comprising aplurality of sectlons, each of said sections comprisin a surfacegenerated by a line one end 0 which pivots at a point at the hearthcenter and the other end follows an outer helical curve at the peripheryof the hearth, said outer curve IlSlIlg as it winds in a direction 0posite to the direction of rotation of t e hearth.

3. A revolving hearth for gas generators and other furnaces provided onits upper face with projections causing the fuel to be raised during therotation of the hearth, each projection comprising a distorted surfacethe generating lines of which bear on the one hand on a point of theaxis of rotation of the hearth and on the other hand on a peripheralhelical type curve rising as it winds in a direction opposite to thedirection of rotation of the hearth.

4. A revolving hearth for gas generators and other furnaces provided onits upper face with projections causing the fuel to be raised during therotation of the hearth, each projection comprising a distorted surfacethe generating ines of which bear on the one hand on a int of the axisof rotation of the hearth and on the other hand on a peripheral helicalcurve rising as it winds in a direction 0 posite to the direction ofrotation of the earth, said hearth having ash discharging passagesdistributed over the surface, the passa es bein inclined towards thecenter of t e heart In testimony whereof I affix my signature.

LEON TREFOIS.

